Re: [PATCH 5/7] nouveau/gsp: fix vblank interrupts on GB20x

[lyude@redhat.com]

On Wed, 2026-08-19 at 00:02 +0400, Mohamed Ahmed wrote:
> On Tue, Aug 18, 2026 at 2:59 AM <lyude@redhat.com> wrote:
> > 
> > On Sat, 2026-08-15 at 03:57 +0400, Mohamed Ahmed wrote:
> > > 
> > > +
> > > +static const struct nvkm_head_func
> > > +gb202_head = {
> > > +     .state = r535_head_state,
> > > +     .vblank_get = gb202_head_vblank_get,
> > > +     .vblank_put = gb202_head_vblank_put,
> > > +};
> > > +
> > 
> > You should probably add these two as well:
> > 
> >         .state = gv100_head_state,
> >         .rgpos = gv100_head_rgpos,
> > 
> > I don't think they've actually changed in blackwell, but it's
> > possible
> > maybe they do change in GB200x so you probably want to double check
> > so
> > we don't lose precise vblank timestamps again.
> > 
> The head state changed actually (but RG position didn't), so adding
> this in would be a regression. I have some work to wire it up
> properly
> (part of VRR bringup) but I wasn't sure whether to include it in this
> series or not. We don't have precise vblank timestamps for anything
> GSP atm and everything falls back to the interrupt path, so it would
> technically be a new feature rather than fix ups.

Actually we definitely do now! We didn't used to for ages, but I wrote
a patch that got upstreamed for it a few weeks ago, you can see it
here:

static const struct nvkm_head_func
r535_head = {
	.state = gv100_head_state,
	.rgpos = gv100_head_rgpos,
	.vblank_get = r535_head_vblank_get,
	.vblank_put = r535_head_vblank_put,
};

If the patch for adding this to blackwell is already ready I wouldn't
mind taking it as part of this series, but that's up to you

> > >  static struct nvkm_conn *
> > >  r535_conn_new(struct nvkm_disp *disp, u32 id)
> > >  {
> > > @@ -1496,6 +1523,20 @@ r535_disp_intr(struct nvkm_inth *inth)
> > >       return IRQ_HANDLED;
> > >  }
> > > 
> > > +static irqreturn_t
> > > +gb202_disp_intr(struct nvkm_inth *inth)
> > > +{
> > > +     struct nvkm_disp *disp = container_of(inth, typeof(*disp),
> > > engine.subdev.inth);
> > > +     irqreturn_t ret = r535_disp_intr(inth);
> > > +
> > > +     /* The FE interrupt vectors are message-based on NVD5.0.
> > > Re-
> > > arm the
> > > +      * low-latency vector so it fires again for any event that
> > > latched
> > > +      * while we were servicing.
> > > +      */
> > > +     nvkm_wr32(disp->engine.subdev.device, 0x611f34,
> > > 0x00000001);
> > > +     return ret;
> > > +}
> > > +
> > >  static void
> > >  r535_disp_fini(struct nvkm_disp *disp, bool suspend)
> > >  {
> > > @@ -1568,7 +1609,9 @@ r535_disp_oneinit(struct nvkm_disp *disp)
> > >       struct nvkm_device *device = disp->engine.subdev.device;
> > >       struct nvkm_gsp *gsp = device->gsp;
> > >       const struct nvkm_rm_api *rmapi = gsp->rm->api;
> > > +     const struct nvkm_rm_gpu *gpu = gsp->rm->gpu;
> > >       NV2080_CTRL_INTERNAL_DISPLAY_WRITE_INST_MEM_PARAMS *ctrl;
> > > +     nvkm_inth_func intr_func;
> > >       unsigned long mask;
> > >       int ret, i;
> > > 
> > > @@ -1722,7 +1765,12 @@ r535_disp_oneinit(struct nvkm_disp *disp)
> > >               nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
> > > 
> > >               for_each_set_bit(i, &disp->head.mask, disp-
> > > >head.nr)
> > > {
> > > -                     ret = nvkm_head_new_(&r535_head, disp, i);
> > > +                     const struct nvkm_head_func *func =
> > > &r535_head;
> > > +
> > > +                     if (gpu->disp.class.root >= GB202_DISP)
> > > +                             func = &gb202_head;
> > > +
> > > +                     ret = nvkm_head_new_(func, disp, i);
> > >                       if (ret)
> > >                               return ret;
> > >               }
> > > @@ -1766,12 +1814,21 @@ r535_disp_oneinit(struct nvkm_disp *disp)
> > >       if (ret)
> > >               return ret;
> > > 
> > > -     ret = nvkm_gsp_intr_stall(gsp, disp->engine.subdev.type,
> > > disp->engine.subdev.inst);
> > > +     if (gpu->disp.class.root >= GB202_DISP) {
> > > +             /* GB20x deliver head-timing interrupts on the
> > > display's
> > > +              * separate low-latency vector (interrupt table
> > > instance 1).
> > > +              */
> > > +             ret = nvkm_gsp_intr_stall(gsp, disp-
> > > > engine.subdev.type, 1);
> > > +             intr_func = gb202_disp_intr;
> > > +     } else {
> > > +             ret = nvkm_gsp_intr_stall(gsp, disp-
> > > > engine.subdev.type, disp->engine.subdev.inst);
> > > +             intr_func = r535_disp_intr;
> > > +     }
> > >       if (ret < 0)
> > >               return ret;
> > > 
> > >       ret = nvkm_inth_add(&device->vfn->intr, ret,
> > > NVKM_INTR_PRIO_NORMAL, &disp->engine.subdev,
> > > -                         r535_disp_intr, &disp-
> > > > engine.subdev.inth);
> > > +                         intr_func, &disp->engine.subdev.inth);
> > >       if (ret)
> > >               return ret;
> > > 
> > > diff --git
> > > a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r570/gsp.c
> > > b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r570/gsp.c
> > > index 996941c668ba..2590b22663cb 100644
> > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r570/gsp.c
> > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r570/gsp.c
> > > @@ -44,6 +44,14 @@ r570_gsp_xlat_mc_engine_idx(u32 mc_engine_idx,
> > > enum nvkm_subdev_type *ptype, int
> > >               *ptype = NVKM_ENGINE_DISP;
> > >               *pinst = 0;
> > >               return true;
> > > +     case MC_ENGINE_IDX_DISP_LOW:
> > > +             /* GB20x+ report a separate low-latency display
> > > vector, used
> > > +              * for head-timing interrupts. Expose it as a
> > > second
> > > DISP
> > > +              * interrupt instance.
> > > +              */
> > > +             *ptype = NVKM_ENGINE_DISP;
> > > +             *pinst = 1;
> > > +             return true;
> > >       case MC_ENGINE_IDX_CE0 ... MC_ENGINE_IDX_CE19:
> > >               *ptype = NVKM_ENGINE_CE;
> > >               *pinst = mc_engine_idx - MC_ENGINE_IDX_CE0;
> >